Сверхкритическая флюидная СО₂ экстракция тория из "черных" песков Азовского моря

Abstract

Natural emissions of black sands on the coast of the Azov Sea contain more than 0.1% of thorium. This has a negative radiation impact on humans and at the same time is a source of thorium, capable of replacing uranium as fuel for both water-water nuclear reactors and prospective types of reactors. Supercritical carbon dioxide fluid extraction of thorium from sand is a promising and not expensive method of solving the environmental problem and obtaining raw nuclear materials. Due to the simple scaling of the method of supercritical fluid extraction and reasonable efficiency even at moderate fluid parameters (20 MPa and 40°C) it is possible to use mobile units on the shore excluding the transport of sand. Extremely small quantities of reagents and process waste, carbon dioxide recovery and ecological compatibility of the technology make it possible to return the cleaned sand directly to the shore. Determination of thorium in sand before and after extraction was performed by spectrophotometric method using arsenazo-3 dye. To calibrate the measurement, a thorium solution with a reextraction to tributyl phosphate from nitric acid was prepared. This made it possible to separate thorium from other elements that give a color reaction with arsenazo-3. The optimum total amount of reagents during extraction was 350 μl per 1 gram of sand. The maximum extraction efficiency of thorium in 24% or 300 μg was achieved by using benzene as an additional reagent.